Regia, Aqua

Aqua regia, or King's water, is a potent mixture of hydrochloric and nitric acid. Called aqua regia due to its ability to dissolve gold and platinum, when neither constituant can do so alone.
When German forces invaded Denmark in WWII the chemist George de Hevesy dissolved the Nobel medallions of German physicists Max von laue and James Frand in aqua regia to prevent their confiscation by the invaders. De hevesy stored the resultant solution on the lab shelf where it was ignored by the German forces. After the war de Heversey returned to the lab to find the bottles untouched. He dropped the gold out of solution and returned the precious metal powder to the Royal Swedish Academy of Sciences and the Nobel Foundation. The foundation recast the medals and presented them to Lue and Frank.

It kind of reminds me of how Lord Florey hid spores of Penicillium in his coat (as in inoculated into his actual coat fibres, thus making the subterfuge completely undetectable) in case England was invaded by German forces in WWII. The plan was to escape to friendlier territories with the spores after destroying all the research and restart penicillin production.

Max von Laue, winner of the physics prize in 1914 “for his discovery of the diffraction of X-rays by crystals”
James Franck, winner of the physics prize in 1925, jointly with Gustav Ludwig Hertz “for their discovery of the laws governing the impact of an electron upon an atom”

The chemist was Georgy de Hevesy, who went on to win the chemistry prize in 1943 “for his work on the use of isotopes as tracers in the study of chemical processes”

The medals had been sent to Niels Bohr at the institute of physics in Copenhagen for safekeeping so as not to be confiscated by the regime in Germany.
With the invasion they were no longer safe in Copenhagen. Niels Bohr was high-profile and Jewish so the institute was an obvious target. This was the means by which the medals were kept out of the invading German's hands.